Interactions of an asymmetric amine with a non-C2 symmetric Cu-salen complex: An EPR/ENDOR and HYSCORE investigation

Caretti, Ignacio, Carter, Emma ORCID: https://orcid.org/0000-0001-6691-2377, Fallis, Ian Andrew ORCID: https://orcid.org/0000-0001-7361-0182, Murphy, Damien Murphy ORCID: https://orcid.org/0000-0002-5941-4879 and Van Doorslaer, Sabine 2011. Interactions of an asymmetric amine with a non-C2 symmetric Cu-salen complex: An EPR/ENDOR and HYSCORE investigation. Physical Chemistry Chemical Physics 13 (45) , pp. 20427-20434. 10.1039/c1cp22522g

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Abstract

Single enantiomers of R-/S-methylbenzylamine (MBA) were found to selectively form adducts with the chiral non-C2 symmetric Cu–salen complex N-(3,5-di-tert-butylsalicylidene)-N′-(salicylidene)-cyclohexane-1,2-diamine copper(II), hereafter labelled [Cu(3)]. The g/A spin Hamiltonian parameters of this Cu(II) complex showed a decrease in symmetry from axial to rhombic upon formation of the [Cu(3)] + MBA adducts. The selectivity in enantiomeric discrimination was found to be only 59 ± 5% in favour of the heterochiral R,R′-[Cu(3)] + S-MBA and S,S′-[Cu(3)] + R-MBA adducts. This was directly evidenced by W-band EPR spectroscopy. The observed low selectivity for enantiomer discrimination is primarily attributed to the loss of the bulky tert-butyl groups from the 3,5 positions of [Cu(3)] compared to the parent N,N′-bis(3,5-di-tert-butylsalicylidene)-cyclohexane-1,2-diamine copper(II) ligand (labelled [Cu(1)]). The structure of the [Cu(3)] complex in the presence and absence of coordinating amine was further investigated by analysis of the ligand hyperfine interactions, as revealed through Q-band CW-ENDOR, X-band Davies ENDOR and HYSCORE. 1H couplings from the –NH2 group of the amine, observed by ENDOR and HYSCORE, provided direct evidence of amine coordination.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry
Subjects:	Q Science > QD Chemistry
Publisher:	Royal Society of Chemistry
ISSN:	1463-9076
Funders:	EPSRC
Last Modified:	03 Dec 2022 11:48
URI:	https://orca.cardiff.ac.uk/id/eprint/14481

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